The present invention relates to a method of and a device for self-adapting feeding forward a disturbance variable in a regulating system, particularly in an air charge regulator for idling speed of an internal combustion engine.
In many applications of regulation technology it is conventional to determine certain variables such as values or positions by a regulating or controlling method in which regulating variables, usually electrical signals having a predetermined functional course, are supplied by a regulator which processes certain input signals fed back from a regulating path so as to include in its regulating behavior the results of regulation on the adjustment of a final setting member. The regulator possesses certain operational characteristics which depending on the application are usually designated as a P-behavior (proportional regulator) or I-behavior (integral regulator) or as a D-behavior (regulator with delay).
In many cases the reaction of the regulators is frequently cumbersome or slow, particularly when in the range of the regulating path, disturbing variables are received. As a consequence, at least undesired oscillations of the regulated actual value will result and these disturbances are also enhanced by the dead time of the regulating system.
In order to achieve that the regulator acts as fast as possible on disturbance, it has been known to provide a so-called feeding forward or disturbance value switching-in measure by means of which a constant or preset disturbance signal is applied immediately in response to the occurrence of a disturbance variable and not in response to the change of the actual value of the regulated magnitude which produces a counter-acting signal at the output of the regulator. In a known circuit for feeding forward a disturbance variable, depending on the output of an evaluation stage "disturbance value yes/no", immediately a change of the output signal from the regulator is produced before the regulator can detect the effect of the disturbance variable on the actual value of the regulated magnitude.
A problem encountered in this known disturbance variable forward feeding circuit is the fact that the value of the disturbance may undergo a change in the course of time. This change even if anticipated and known within certain limits, cannot be taken into account and the regulator does not react thereon.
Therefore a need was felt to provide a regulating method or a device for an adaptive forward feeding of a disturbance variable in a regulator which would be capable of an automatic correction of the changes in the disturbance variables caused by external conditions, for example.
The following considerations relate specifically to situations in a so-called idling speed air charge regulators in internal combustion engines, for which the present invention is particularly suitable. It will be understood however that this invention is not limited to idling speed air charge regulation but is applicable also for any regulating process in which it is desirable to provide a rapid reaction to the occurrence of a disturbance and accordingly in which the before mentioned forward feeding of a disturbance signal is applicable.
In an idling speed air charge regulation as known, the disturbances occur for example during the switching-on of an air conditioner or after an automatic transmission shifts from a neutral position in a driving stage. In both instances considerable loads with corresponding rotary speed changes are produced. These sudden loads must be quickly intercepted especially in the idling speed range operating at the relatively low rotary speed. Furthermore, it must be taken into account that such disturbance variables may cause strongly fluctuating loads, for example in the case of an air conditioner the load changes in response to momentary external temperatures or to the setting of an internal thermostat.